A drilling riser is made up of an assembly of tubular elements of length ranging between 15 and 27 m (50 and 90 feet), assembled by connectors. The tubular elements generally consist of a main tube provided with a connector at each end. Tubular auxiliary lines, also called peripheral lines, commonly referred to as “kill line”, “choke line”, “booster line” and “hydraulic line”, allowing circulation of technical fluids, are provided parallel to the main tube. The tubular elements are assembled on the drilling site, from a floater. The riser is lowered into the water depth as the tubular elements are assembled, until it reaches the wellhead located on the sea bottom.
In the perspective of drilling at water depths that can reach 3500 m or more, the weight of the riser becomes very penalizing. This phenomenon is increased by the fact that, for the same maximum working pressure, the length of the riser requires a larger inside diameter for the auxiliary lines, considering the necessity to limit pressure drops.
Besides, the necessity to decrease the riser assembly time is all the more critical since the water depth, and therefore the riser length, is great.
A riser intended for other applications, notably production, completion or workover, also consists of an assembly of tubular elements assembled by connectors.
Documents FR-2,925,105, FR-2,956,693 and FR-2,956,694 describe various solutions notably aiming to involve the auxiliary lines, together with the main tube, in the taking up of the longitudinal stresses applied to the riser. However, for the systems described in these patents, fastening of the auxiliary lines with respect to the main tube causes tensile stresses in the auxiliary lines. In order to withstand these tensile stresses, the auxiliary lines have great thickness values, which generates an increase in the mass and size of the floats, and therefore in the cost of the riser. Another problem with these connectors concerns the inspection and maintenance of the locking ring. Indeed, the locking rings in the aforementioned patents are not fully removable. It is therefore not possible to inspect the entire locking ring.
To overcome this problem, patent applications WO-2015/071,411 and WO-2015/169,560 relate to connectors provided with locking rings removable by means of two bayonet connections. However, these two connectors require a particular layout for the studs to prevent simultaneous disconnection of the ring with the two riser sections.
The present invention describes a solution providing a compact connector design with a locking ring surrounding the main tube elements. The connector according to the invention comprises a locking ring allowing a bayonet type connection on either side with two riser sections, by means of studs having identical angular ranges. Besides, the connector comprises at least one removable pin for translationally blocking the locking ring, notably upon locking and unlocking. Thus, the connector according to the invention is removable, and simultaneous removal of the ring with the two riser sections is prevented. Furthermore, the dimensions of the ring (inside diameter nearly identical to the outside diameter of the main tube elements) allow the locking ring to be positioned as close as possible to the main tube elements, which provides connector compactness.